#include <stdio.h>
#include <cs50.h>
#include <string.h>
//for character classification functions
#include <ctype.h>

//function declaration
bool validate(string key);

//global variable
string abc = "abcdefghijklmnopqrstuvwxyz";

int main(int argc, string argv[])
{
    string key = NULL, plaintext = NULL, ciphertext = NULL; //Create variable outside if statement. Otherwise if the statement isn't true the variable isn't created for later use.
    int length; //Generally good practice to create all your variables at the top and only create variables that only need to be used once within your loops.

    if (argc == 2)
    {
        key = toupper(argv[1]); //Keeping the key as uppercase.
    }
    else
    {
        printf("Usage: ./substitution key \n");
        return 1;
    }

    if (!validate(key)) //No need to write == true, just putting a function in brackets like (validate(key)) is checking if it returns true, the ! checks if it's false, just a small change to help with readability.
    {
        printf("Key must contain 26 unique characters\n");
        return 1;
    }

    plaintext = get_string("plaintext: ");
    length = strlen(plaintext);

    for(int i = 0; i < length; i++)
    {
        if (isupper(plaintext[i]) != 0)
        {
            for (int j = 0; j < 26; j++ )
            {
                if (abc[j] == tolower(plaintext[i])) //Problem is how you're handling copying your arrays.
                {
                    ciphertext[i] = toupper(key[j]);
                    break;
                }
            }
        }
        else if (islower(plaintext[i]) != 0)
        {
            for (int j = 0; j < 26; j++ )
            {
                if (abc[j] == plaintext[i])
                {
                    ciphertext[i] = tolower(key[j]);
                    break;
                }
            }
        }
        else
        {
            ciphertext[i] = plaintext[i];
        }
    }
    printf("ciphertext: %s\n", ciphertext);
    return 0;
}

bool validate(string key)
{
    int match_counter = 0;
    if (strlen(key) == 26)
    {
        for (int i = 0; i < 26; i++)
        {
            for (int j = 0; j < 26; j++)
            {
                if(tolower(key[j]) == abc[i])
                {
                    match_counter++;
                    break;
                }
            }
        }

        if(match_counter == 26)
        {
            return true;
        }
        else
        {
            return false;
        }
    }
    else
    {
        return false;
    }
}